Ooooookkkkaaaaayyyy..... So. I am going to take this one from the top and go really slow so everyone who reads my posts can understand. Full disclaimer before I start. I am an i200 PLD, i197 WAR, and i193 DrK. I have raided with all three tanks and have been around FF14 from 1.0. I have a VERY good grasp at tanking and MMOs in general and do not shy away from the fact that I will play the best possible tank for my static.
So the tank meta in FF14 is based primarily around scripted burst damage, scripted/timed mechanics, and DPS enrage timers. This means that when the tanks were being designed they were given (after patches and buffs) the ability to MT and OT every single encounter. So that being said each tank has the ability in some way to survive/effectively tank each encounter. So because the fights are based around actual enrages and not healer MP strain/drought personal mitigation is an absolute moot point. Anything more than bare minimum is a waste. This is very similar to VIT in this respect.
So what we are left with when looking at tanks is three categories of use: Raid DPS increase via debuffs, Personal DPS, and Raid Mitigation. Everything, and I mean absolutely everything, aside from those 3 categories is moot. So because the developers want each tank to be able to preform in the MT and OT role then each tank SHOULD possess some way to contribute to each of those categories. Currently only one tank does, which is the WAR. THIS DOES NOT MEAN WAR IS OVERPOWERED! It means that WAR is actually designed correctly for the current tanking meta of FF14. When looking at the other two tanks it is obvious that they are not very well designed. PLD offers absolutely nothing to a raid except ease of use (which if you are Savage raiding should not be something you care about), and DrK has so many shoehorned abilites it will make your head hurt trying to find a roll for them. WAR is so well designed in fact that SE needs to buff the two current tanks to be equally beneficial to their raid groups or they will wither away and die when LB gauges are a non issue for clears.
So once again, WAR is not overpowered. PLD and DrK are just horribly designed for the current (and past, and most likely future) of the tanking meta of FF14 and NEED to be buffed/redesigned.